Crude oil is typically pumped from underground reservoirs using a mechanical pumping unit which drives or powers a reciprocating string of sucker rods to actuate a subsurface pump. A well head assembly at the surface may include various components such as a tubing head, a pressure regulator, a blowout preventer, a stuffing box assembly, a polished rod lubricator, and a rod rotator. The stuffing box assembly seals with the reciprocating polished rod passing therethrough to prevent the well bore fluids from being vented to the atmosphere. The stuffing box assembly may be lubricated to ease the movement of the polished rod through the stuffing box and help prevent wear on the seals used to provide the sliding packoff with the polished rod. Other wells are pumped using a rotating rather than a reciprocating rod string, and a stuffing box assembly is also provided for sealing with this rotating rod string.
The makeup and design of a stuffing box assembly usually depends upon its use in either normal or difficult pumping situations. Under normal pumping conditions, a stuffing box may be connected to a blowout preventer at its lower end and an upper lubricating gland may be attached at its upper end to wipe the lubricating fluid from the polished rod as the rod passes through the stuffing box assembly, thereby retaining the lubricating fluid within the upper lubricating gland. Under difficult or abnormal pumping conditions, the upper lubricating gland may be replaced above the stuffing box with an oil reservoir gland or stuffing box gland which includes a fluid reservoir of lubricant that the polished rod moves freely through for lubricating and cooling the polished rod. Excess lubricant coated on the polished rod is retained within the oil reservoir gland by a wiper assembly similar to that of the upper lubricating gland to wipe the polished rod clean of any excess lubricant as it moves through the oil reservoir gland. However, much of the lubricant is typically lost or transmitted through the oil reservoir gland to the stuffing box due to a number of variables, such as gravity, movement of the polished rod and weak sealing engagement between the oil reservoir gland and stuffing box. Consequently, lubricant contained in the oil reservoir gland must often be replaced, causing unnecessary expense and delay. If the lubricant is not frequently replaced, the oil reservoir gland runs dry, thereby contributing to high wear between the moving polished rod and the stuffing box packing and, if not corrected, to high leakage of fluid past the stuffing box.
A polished rod lubricator may be installed as part of the stuffing box assembly under difficult or abnormal pumping conditions. The polished rod lubricator normally includes a pair of hinged fluid reservoirs that surround the polished rod and store a lubricant. The polished rod lubricator also includes an absorbent wick communicating between an absorbent pad and the lubricant in the fluid reservoir in order to control the rate of lubrication of the polished rod as it contacts the absorbent pad. Despite the use of various stuffing box assemblies, uniform and consistent lubrication of the polished rod remains problematic.
The foregoing disadvantages of the prior art are overcome by the present invention, which provides a relatively simple and highly reliable stuffing box gland capable of both cooperating with a stuffing box positioned below the stuffing box gland to compressively seal the packing within a stuffing box, and maximize retention of a lubricant within a fluid reservoir of the stuffing box gland for uniform and consistent lubrication of the polished rod as it moves relative to the stuffing box gland.